Rivatuner allows you to control the fan speed. It is a bit loud when running adaquately. I usually run it at 90-100% when gaming, leave it on 60% or so the rest of the time. It usually defaults on like 27%, which will cause your gpu to overheat when gaming. Like Christine said, you could get a passive colling solution which would alliviate the noise problem. If you do want to do step up, if you put the old cooler back on evga will still accept the step-up.

As far as prime goes, you can definately use it to test max temps and stability, but honestly it works your proc more than you ever will in normal circumstances, so I don't really ever worry about it. I just run it for a bit if I'm not sure if my oc is stable. The stress it puts on the cpu is not really worth pulling an all-nighter to me, as it just wears down the proc more than it would normally.